Praying For Other's Salvation

I have two friends that I have prayed for for their salvation, and whilst I have not seen about the end result yet and whether it is a positive one, I can tell you that it seems Heaven does signpost that work is happening with the people you love and care about when you pray for them.

There is freedom of will of course and in which case you do your best to partner with God or to ask for His help but you accept the outcome even if the possibility is there that that person decides not to believe.